Generally, if a printing apparatus is connected to a computer and print is executed by means of the printing apparatus following a print instruction from the computer, the operator needs to turn on each power supply of the computer and the printing apparatus before the print is started because the power turning ON/OFF section of the computer and the power turning ON/OFF section of the printing apparatus are provided individually. Although this is not so serious problem if the computer and the printing apparatus are provided in the vicinity, if it is connected via the network, the operator sometimes sends a print instruction without noticing that the power of the printing apparatus is turned OFF, resulting in wasting of time, or there is inconvenience in turning ON the power supply located far away.
For example, patent document 1 has disclosed a method capable of automatically turning ON the power switch of the printing apparatus by detecting a connection between a host unit and a printing apparatus. If the host unit and the printing apparatus are connected to each other through a USB connection, whether or not the USB cable is connected to the connector of the unit main body is checked by detecting rising or falling of the data line of the USB cable in a predetermined time period, and if the connection is detected, power ON processing is executed.
[Patent Document 1] Japanese Patent Application Laid-Open No. 2002-178610